Aligning vehicle wheels within specific tolerances is important for optimal control of the vehicle and for consistent wear of the tires. Alignment is performed primarily by adjusting camber, caster, toe, and steering axis inclination of the wheels.
The toe angle of a vehicle is the angle of the centerline of a front wheel relative to the longitudinal centerline of the vehicle when viewed from above. In three-wheeled vehicles having two front wheels, the toe angle of both wheels must be determined relative to the single rear wheel. This ensures the vehicle tracks correctly relative to the drive wheel, and demonstrates stable ride characteristics. The toe setting of the wheels, in particular, must be measured and aligned in order to ensure proper driving characteristics, improve fuel efficiency, and reduce tire wear.
In particular, proper toe angle relative to vehicle specifications ensures directional stability. In passenger vehicles, for example, the toe angle setting is used to maintain straight-line stability of the vehicle and enable the vehicle to resist road inputs such as bumps, potholes, and the like. In the extreme cases, a vehicle that has improper toe settings may steer the vehicle at an angle offset from the direction the driven wheel(s) point, a condition known as “dogtracking.”
In four wheel vehicle alignment systems, the vehicle is typically driven onto a hydraulic lift and elevated. Target elements are attached to the vehicle wheels, and an external fixed sensor system detects the position and orientation of the target elements. The technician then adjusts the toe angle of the front wheels based on the sensed position of the wheels. However, since the rear wheel in a three-wheeled vehicle is centered behind the body of the vehicle, the rear wheel is typically obscured from view of the sensor system. When doing a four wheel alignment, the purpose is to ensure proper thrust angle and align each front wheel directly in front of the corresponding rear wheel. In a three wheeled vehicle, however, it is not possible to align the front wheels directly in front of the corresponding rear wheel since there is only a single rear wheel. Additionally, sensor based toe alignment systems are very expensive.
One solution to aligning three-wheeled vehicles involves attaching a laser to the front wheels and pointing the laser at targets positioned around the vehicle. The targets are set on the ground, and manually arranged so as to be positioned relative to the front and rear wheels. Based on the relative positions of the laser on the targets, the technician aligns the vehicle to bring the alignment settings within the specifications.
This solution requires substantial time for the technician to place and precisely measure the positions of the targets. Since vehicle toe angles are measured to very small tolerances, even a minute misalignment of the target results in the toe angle being improperly aligned. Thus, the manual setting of the toe angle targets has very low precision and substantial potential for user error. In addition to error on individual settings, this solution suffers from reduced repeatability from measurement to measurement, even when performed by the same technician.
What is needed, therefore, is a wheel alignment system for a three-wheeled vehicle that enables precise determination and alignment of the toe angle of the front wheels with respect to the rear wheels with limited potential for user error.